1. Field of the Invention
The present invention relates to a wireless IC device, and particularly, to a wireless IC device used for an RFID (Radio Frequency Identification) system, and a component used for the wireless IC device.
2. Description of the Related Art
In recent years, for an inventory item management system, an RFID system has been developed which includes a reader/writer for generating a dielectric magnetic field and an IC tag (hereafter, referred to as wireless IC device) for storing predetermined information about an inventory item which communicate with one another via a non-contact method, thereby transmitting information. Known wireless IC devices used in RFID systems are described in Japanese Unexamined Patent Application Publication No. 2005-136528 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2005-244778 (Patent Document 2), for example.
The wireless IC device shown in FIG. 59 includes an antenna pattern 301 provided on a plastic film 300, and a wireless IC chip 310 is attached to one end of the antenna pattern 301, and the wireless IC device shown in FIG. 60 includes an antenna pattern 321 and a radiation electrode 322 provided on a plastic film 320, and a wireless IC chip 310 is attached to a predetermined portion of the antenna pattern 321.
However, with the conventional wireless IC devices, the wireless IC chip 310 is connected to and mounted on the antenna pattern 301 or 321 using an Au bump in a DC manner. Thus, it is necessary to determine the position of the small wireless IC chip 310 on the film 300 or 320 having a large area. However, it is extremely difficult to mount the wireless IC chip 310 on the large-area film 300 or 320. Thus, positional deviation at the time of mounting causes the resonant frequency properties at the antenna to be changed. The resonant frequency properties at the antenna are also changed by the antenna pattern 301 or 321 being rounded, or being sandwiched between dielectric members (e.g., inserted into a book).